Thread rolling heads can be, for example, axial thread rolling heads or radial thread rolling heads. They can have, for example, three profile rollers uniformly distributed about an insertion section. A workpiece, cylindrical for example, can be inserted in the longitudinal direction into the insertion section. With axial thread rolling heads, machining (that is, forming the threads) on the workpiece occurs in the course of insertion into the insertion section. With radial thread rolling heads, the profile rollers for machining are positioned radially onto the workpiece after the insertion of the workpiece. Generally, there is an opening mechanism with which the profile rollers can be displaced between a machining position and an open position, in which they are displaced radially outward. After the machining process, the rollers are moved into the open position, and the thread rolling head can be removed from the workpiece without collision.
For adapting to different workpieces to be machined, and also for precise adjustment, it is frequently necessary to adapt the cross-section of the insertion section in the machining position of the profile rollers by adjusting the spacing of the profile rollers to each other. Different solutions to this problem have been attempted. From German document DE 4430184 C2, for example, a bearing housing of an axial thread rolling head comprises two housing parts that can rotate relative to each other. The spacing of the profile rollers in the machining position can be changed by manually rotating the housing parts relative to each other. A gearing mechanism is provided between the housing parts that can rotate relative to each other, which translates the relative rotation between the housing parts into a corresponding change in the spacing of the profile rollers. It is possible to rotate the housing parts after loosening a clamp. A similar solution is attempted in International document WO 2005/102557 A2.
Radial displacement of profile rollers is shown in German document DE 9002822 U1.